Modeling the impact of vaccination control strategies on a foot and mouth disease outbreak in the Central United States

The central United States (U.S.) has a large livestock population including cattle, swine,sheep and goats. Simulation models were developed to assess the impact of livestock herdtypes and vaccination on foot and mouth disease (FMD) outbreaks using the North Amer-ican Animal Disease Spread Model. In this study, potential FMD virus outbreaks in thecentral region of the U.S. were simulated to compare different vaccination strategies to adepopulation only scenario. Based on data from the U.S. Department of Agriculture NationalAgricultural Statistics Service, a simulated population of 151,620 livestock operations char-acterized by latitude and longitude, production type, and herd size was generated. For thesimulations, a single 17,000 head feedlot was selected as the initial latently infected herdin an otherwise susceptible population. Direct and indirect contact rates between herdswere based on survey data of livestock producers in Kansas and Colorado. Control meth-ods included ring vaccination around infected herds. Feedlots ≥3000 head were either theonly production type that was vaccinated or were assigned the highest vaccination priority.Simulated vaccination scenarios included low and high vaccine capacity, vaccination zonesof 10 km or 50 km around detected infected premises, and vaccination trigger of 10 or 100detected infected herds. Probability of transmission following indirect contact, movementcontrols and contact rate parameters were considered uncertain and so were the subjectsof sensitivity analysis. All vaccination scenarios decreased number of herds depopulatedbut not all decreased outbreak duration. Increased size of the vaccination zone during anoutbreak decreased the length of the outbreak and number of herds destroyed. Increasedsize of the vaccination zone primarily resulted in vaccinating feedlots ≥3000 head acrossa larger area. Increasing the vaccination capacity had a smaller impact on the outbreakand may not be feasible if vaccine production and delivery is limited. The ability to vac-cinate all the production types surrounding an infected herd did not appear as beneficialas priority vaccination of feedlot production types that have high numbers of indirect con-tacts. Outbreak duration, number of herds depopulated and the effectiveness of vaccinationwere sensitive to indirect contact transmission probability and movement restrictions. Theresults of this study will provide information about the impacts of disease control protocolswhich may be useful in choosing the optimal control methods to meet the goals of rapideffective control and eradication.© 2014 Elsevier B.V. All rights reserved.